If you're bored with the same old rivers, head to Colombia where you can see something that looks like the end result of a collaboration between James Cameron, Timothy Leary, and a box full of melted crayons.
Travel east of the Andes and you'll find Los Llanos, a massive portion of open grasslands. It's home to Caño Cristales, a river often called the "Liquid Rainbow." The jaw-dropping collision of colors is caused by macarenia clavigera, aquatic plants unique to the body of water that shine brightly through the surface in various colors. The 62-mile stretch of water is as gorgeous as it is delicate.